Implement string interpolation up to SSA.

dart/frog/leg/tree/visitors.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 class AbstractVisitor<R> implements Visitor<R> {
   abstract R visitNode(Node node);
 
   R visitBlock(Block node) => visitStatement(node);
   R visitClassNode(ClassNode node) => visitNode(node);
   R visitConditional(Conditional node) => visitExpression(node);
@@ skipping 18 matching lines @@
   R visitOperator(Operator node) => visitIdentifier(node);
   R visitParenthesizedExpression(ParenthesizedExpression node) {
     return visitExpression(node);
   }
   R visitPostfix(Postfix node) => visitNodeList(node);
   R visitPrefix(Prefix node) => visitNodeList(node);
   R visitReturn(Return node) => visitStatement(node);
   R visitSend(Send node) => visitExpression(node);
   R visitSendSet(SendSet node) => visitSend(node);
   R visitStatement(Statement node) => visitNode(node);
+  R visitStringInterpolation(StringInterpolation node) => visitExpression(node);
+  R visitStringInterpolationPart(StringInterpolationPart node) {
+    return visitNode(node);
+  }
   R visitThrow(Throw node) => visitStatement(node);
   R visitTypeAnnotation(TypeAnnotation node) => visitNode(node);
   R visitVariableDefinitions(VariableDefinitions node) => visitStatement(node);
   R visitWhile(While node) => visitLoop(node);
 }
 
 /**
  * This visitor takes another visitor and applies it to every
  * node in the tree. There is currently no way to control the
  * traversal.
@@ skipping 33 matching lines @@
   visitNewExpression(NewExpression node) {}
   visitNodeList(NodeList node) {}
   visitOperator(Operator node) {}
   visitParenthesizedExpression(ParenthesizedExpression node) {}
   visitPostfix(Postfix node) {}
   visitPrefix(Prefix node) {}
   visitReturn(Return node) {}
   visitSend(Send node) {}
   visitSendSet(SendSet node) {}
   visitStatement(Statement node) {}
+  visitStringInterpolation(StringInterpolation node) {}
+  visitStringInterpolationPart(StringInterpolationPart node) {}
   visitThrow(Throw node) {}
   visitTypeAnnotation(TypeAnnotation node) {}
   visitVariableDefinitions(VariableDefinitions node) {}
   visitWhile(While node) {}
 }